思茅和呵叻盆地钾盐矿研究新进展和新认识

思茅盆地与呵叻盆地属于同一大地构造带。二者的含钾盐建造在区域分布、沉积特征、成盐层位、析盐矿物组合特征及物质来源等方面具有良好的可比性,是中国海相找钾实现突破的重要潜在区之一。尽管目前对两地钾盐矿的成矿认识取得了许多进展,但对于二者的关系和成矿模式及规律等还存在着较大争议。为了下一步更好地建立思茅盆地钾盐矿的成矿规律和实现深部找钾的突破,本文从构造背景、地层年代、古气候环境和物质来源等方面对最近一些重要进展和认识做了梳理,现已确定:(1)思茅陆块与印度支那陆块在中生代可能为统一的整体,思茅与呵叻盆地基本位于副热带高压带内,在晚三叠世、中—晚侏罗世和晚白垩世具有较好的成盐成钾构造和古气候条件;(2)思茅和呵叻盆地在含钾盐及其下伏地层沉积期间可能具有相似的潜在物源区,包括扬子、松潘—甘孜、可可西里、义敦、北羌塘和南羌塘陆块等;(3)思茅与呵叻盆地钾盐矿的成钾物质主要来自陆源水体,同时也有海水和深部热液补给;(4)思茅和呵叻盆地含钾盐地层的年代部分重叠,但不完全吻合;(5)勐野井钾盐矿与呵叻钾盐矿可能系非同期矿床。综合构造和气候等证据,推测思茅盆地在约85.0 Ma这一呵叻钾盐矿成矿的时段就可能具有了重要的成钾潜力。

Research progress and new views on the potash deposits in the Simao and Khorat Basins.

The Simao and Khorat Basins belong to the same tectonic zone of the Tethys. The potash deposits in the two basins share similarities in regional distribution, sedimentary characteristics, potassic salt horizon, mineral assemblage and brine source. Therefore, the Simao Basin is believed to be one of the important areas with high exploration potential for marine potash exploration in China. Although significant progress has been made in understanding the formation mechanism of the potash deposits, the relationship between the two basins and the metallogenic model/pattern of potash deposits are still highly debatable. This paper summarized the recent achievements in the tectonic features, stratigraphic chronology, paleoclimate environment and provenance of potash deposits in the two basins to provide a better understanding for future potash metallogenic regularity study and facilitate breakthroughs in potash exploration in the Simao Basin. We believe: (1) The Simao and Indochina terranes might have been a unified terrane in the subtropical high-pressure belt during the Mesozoic, where the Late Triassic, Middle-Late Jurassic and Late Cretaceous were under favorable tectono-climatic conditions for potash formation. (2) The two basins may share similar potential provenance areas, including the Yangtze, Songpan-Ganzi, Hoh Xil, Yidun and North and South Qiangtang terranes. (3) The principal source materials mainly came from a terrestrial water source, with some seawater and deep hydrothermal fluid recharges. (4) The depositional ages of the potash-bearing strata in the two basins only partially overlap rather than contemporaneous. (5) The potash mines in the Simao and Khorat basins might have deposited in different periods. Together with other tectono-climatic evidence, the formation time of the Khorat potash deposit, i.e, ~85.0 Ma, would be another potentially important period to explore for potash deposits in the Simao Basin.